1. Field of the Invention
The present invention relates to an apparatus and a method for washing substrates such as semiconductor wafers and glass substrates for LCDs.
2. Description of the Related Art
In the manufacturing of semiconductor devices, a washing treatment apparatus is employed for removing particles, organic contaminants, metallic impurities and the like from the surfaces of semiconductor wafers by using ammonia, hydrofluoric acid, pure water and the like. In a one-by-one washing treatment apparatus, for example, the surface of a wafer is washed with chemical solutions such as an aqueous ammonia solution and an aqueous hydrofluoric acid solution, and then washed with pure water. In the one-by-one washing treatment apparatus, a wafer is horizontally held by a spin chuck and an aqueous ammonia solution or an aqueous hydrofluoric acid is supplied to a wafer for a predetermined time so as to cover it up.
However, in conventional washing treatment apparatuses, as the temperature of the chemical solution decreases, the reaction rate of the chemical washing (chemical cleaning) reduces. As a result, in some cases, sufficient washing performance is not obtained. To circumvent this, it is conceivable that the supply amount of the chemical solution is increased to make up for the insufficient washing performance. However, the large consumption of the chemical solution required in this method offers a problem in that a treatment cost is inevitably increased.
Furthermore, in the case where an alkaline solution is used together with an acidic solution in the conventional washing treatment apparatuses, the alkaline washing component used in a previous step is brought into the next acidic washing step, together with a wafer. As a result, the washing efficiency decreases.